Merge "Update prebuilt Clang to r353983." into p9.0HEADp9.0-backupp9.0

1 files changed, 1868 insertions, 0 deletions

diff --git a/clang-r353983/include/clang/Basic/SourceManager.h b/clang-r353983/include/clang/Basic/SourceManager.h
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+//===- SourceManager.h - Track and cache source files -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Defines the SourceManager interface.
+///
+/// There are three different types of locations in a %file: a spelling
+/// location, an expansion location, and a presumed location.
+///
+/// Given an example of:
+/// \code
+/// #define min(x, y) x < y ? x : y
+/// \endcode
+///
+/// and then later on a use of min:
+/// \code
+/// #line 17
+/// return min(a, b);
+/// \endcode
+///
+/// The expansion location is the line in the source code where the macro
+/// was expanded (the return statement), the spelling location is the
+/// location in the source where the macro was originally defined,
+/// and the presumed location is where the line directive states that
+/// the line is 17, or any other line.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_BASIC_SOURCEMANAGER_H
+#define LLVM_CLANG_BASIC_SOURCEMANAGER_H
+
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Basic/SourceLocation.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include <cassert>
+#include <cstddef>
+#include <map>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace clang {
+
+class ASTReader;
+class ASTWriter;
+class LineTableInfo;
+class SourceManager;
+
+/// Public enums and private classes that are part of the
+/// SourceManager implementation.
+namespace SrcMgr {
+
+  /// Indicates whether a file or directory holds normal user code,
+  /// system code, or system code which is implicitly 'extern "C"' in C++ mode.
+  ///
+  /// Entire directories can be tagged with this (this is maintained by
+  /// DirectoryLookup and friends) as can specific FileInfos when a \#pragma
+  /// system_header is seen or in various other cases.
+  ///
+  enum CharacteristicKind {
+    C_User, C_System, C_ExternCSystem, C_User_ModuleMap, C_System_ModuleMap
+  };
+
+  /// Determine whether a file / directory characteristic is for system code.
+  inline bool isSystem(CharacteristicKind CK) {
+    return CK != C_User && CK != C_User_ModuleMap;
+  }
+
+  /// Determine whether a file characteristic is for a module map.
+  inline bool isModuleMap(CharacteristicKind CK) {
+    return CK == C_User_ModuleMap || CK == C_System_ModuleMap;
+  }
+
+  /// One instance of this struct is kept for every file loaded or used.
+  ///
+  /// This object owns the MemoryBuffer object.
+  class alignas(8) ContentCache {
+    enum CCFlags {
+      /// Whether the buffer is invalid.
+      InvalidFlag = 0x01,
+
+      /// Whether the buffer should not be freed on destruction.
+      DoNotFreeFlag = 0x02
+    };
+
+    /// The actual buffer containing the characters from the input
+    /// file.
+    ///
+    /// This is owned by the ContentCache object.  The bits indicate
+    /// whether the buffer is invalid.
+    mutable llvm::PointerIntPair<llvm::MemoryBuffer *, 2> Buffer;
+
+  public:
+    /// Reference to the file entry representing this ContentCache.
+    ///
+    /// This reference does not own the FileEntry object.
+    ///
+    /// It is possible for this to be NULL if the ContentCache encapsulates
+    /// an imaginary text buffer.
+    const FileEntry *OrigEntry;
+
+    /// References the file which the contents were actually loaded from.
+    ///
+    /// Can be different from 'Entry' if we overridden the contents of one file
+    /// with the contents of another file.
+    const FileEntry *ContentsEntry;
+
+    /// A bump pointer allocated array of offsets for each source line.
+    ///
+    /// This is lazily computed.  This is owned by the SourceManager
+    /// BumpPointerAllocator object.
+    unsigned *SourceLineCache = nullptr;
+
+    /// The number of lines in this ContentCache.
+    ///
+    /// This is only valid if SourceLineCache is non-null.
+    unsigned NumLines = 0;
+
+    /// Indicates whether the buffer itself was provided to override
+    /// the actual file contents.
+    ///
+    /// When true, the original entry may be a virtual file that does not
+    /// exist.
+    unsigned BufferOverridden : 1;
+
+    /// True if this content cache was initially created for a source
+    /// file considered as a system one.
+    unsigned IsSystemFile : 1;
+
+    /// True if this file may be transient, that is, if it might not
+    /// exist at some later point in time when this content entry is used,
+    /// after serialization and deserialization.
+    unsigned IsTransient : 1;
+
+    ContentCache(const FileEntry *Ent = nullptr) : ContentCache(Ent, Ent) {}
+
+    ContentCache(const FileEntry *Ent, const FileEntry *contentEnt)
+      : Buffer(nullptr, false), OrigEntry(Ent), ContentsEntry(contentEnt),
+        BufferOverridden(false), IsSystemFile(false), IsTransient(false) {}
+
+    /// The copy ctor does not allow copies where source object has either
+    /// a non-NULL Buffer or SourceLineCache.  Ownership of allocated memory
+    /// is not transferred, so this is a logical error.
+    ContentCache(const ContentCache &RHS)
+      : Buffer(nullptr, false), BufferOverridden(false), IsSystemFile(false),
+        IsTransient(false) {
+      OrigEntry = RHS.OrigEntry;
+      ContentsEntry = RHS.ContentsEntry;
+
+      assert(RHS.Buffer.getPointer() == nullptr &&
+             RHS.SourceLineCache == nullptr &&
+             "Passed ContentCache object cannot own a buffer.");
+
+      NumLines = RHS.NumLines;
+    }
+
+    ContentCache &operator=(const ContentCache& RHS) = delete;
+
+    ~ContentCache();
+
+    /// Returns the memory buffer for the associated content.
+    ///
+    /// \param Diag Object through which diagnostics will be emitted if the
+    ///   buffer cannot be retrieved.
+    ///
+    /// \param Loc If specified, is the location that invalid file diagnostics
+    ///   will be emitted at.
+    ///
+    /// \param Invalid If non-NULL, will be set \c true if an error occurred.
+    llvm::MemoryBuffer *getBuffer(DiagnosticsEngine &Diag,
+                                  const SourceManager &SM,
+                                  SourceLocation Loc = SourceLocation(),
+                                  bool *Invalid = nullptr) const;
+
+    /// Returns the size of the content encapsulated by this
+    /// ContentCache.
+    ///
+    /// This can be the size of the source file or the size of an
+    /// arbitrary scratch buffer.  If the ContentCache encapsulates a source
+    /// file this size is retrieved from the file's FileEntry.
+    unsigned getSize() const;
+
+    /// Returns the number of bytes actually mapped for this
+    /// ContentCache.
+    ///
+    /// This can be 0 if the MemBuffer was not actually expanded.
+    unsigned getSizeBytesMapped() const;
+
+    /// Returns the kind of memory used to back the memory buffer for
+    /// this content cache.  This is used for performance analysis.
+    llvm::MemoryBuffer::BufferKind getMemoryBufferKind() const;
+
+    /// Get the underlying buffer, returning NULL if the buffer is not
+    /// yet available.
+    llvm::MemoryBuffer *getRawBuffer() const { return Buffer.getPointer(); }
+
+    /// Replace the existing buffer (which will be deleted)
+    /// with the given buffer.
+    void replaceBuffer(llvm::MemoryBuffer *B, bool DoNotFree = false);
+
+    /// Determine whether the buffer itself is invalid.
+    bool isBufferInvalid() const {
+      return Buffer.getInt() & InvalidFlag;
+    }
+
+    /// Determine whether the buffer should be freed.
+    bool shouldFreeBuffer() const {
+      return (Buffer.getInt() & DoNotFreeFlag) == 0;
+    }
+  };
+
+  // Assert that the \c ContentCache objects will always be 8-byte aligned so
+  // that we can pack 3 bits of integer into pointers to such objects.
+  static_assert(alignof(ContentCache) >= 8,
+                "ContentCache must be 8-byte aligned.");
+
+  /// Information about a FileID, basically just the logical file
+  /// that it represents and include stack information.
+  ///
+  /// Each FileInfo has include stack information, indicating where it came
+  /// from. This information encodes the \#include chain that a token was
+  /// expanded from. The main include file has an invalid IncludeLoc.
+  ///
+  /// FileInfos contain a "ContentCache *", with the contents of the file.
+  ///
+  class FileInfo {
+    friend class clang::SourceManager;
+    friend class clang::ASTWriter;
+    friend class clang::ASTReader;
+
+    /// The location of the \#include that brought in this file.
+    ///
+    /// This is an invalid SLOC for the main file (top of the \#include chain).
+    unsigned IncludeLoc;  // Really a SourceLocation
+
+    /// Number of FileIDs (files and macros) that were created during
+    /// preprocessing of this \#include, including this SLocEntry.
+    ///
+    /// Zero means the preprocessor didn't provide such info for this SLocEntry.
+    unsigned NumCreatedFIDs : 31;
+
+    /// Whether this FileInfo has any \#line directives.
+    unsigned HasLineDirectives : 1;
+
+    /// The content cache and the characteristic of the file.
+    llvm::PointerIntPair<const ContentCache*, 3, CharacteristicKind>
+        ContentAndKind;
+
+  public:
+    /// Return a FileInfo object.
+    static FileInfo get(SourceLocation IL, const ContentCache *Con,
+                        CharacteristicKind FileCharacter) {
+      FileInfo X;
+      X.IncludeLoc = IL.getRawEncoding();
+      X.NumCreatedFIDs = 0;
+      X.HasLineDirectives = false;
+      X.ContentAndKind.setPointer(Con);
+      X.ContentAndKind.setInt(FileCharacter);
+      return X;
+    }
+
+    SourceLocation getIncludeLoc() const {
+      return SourceLocation::getFromRawEncoding(IncludeLoc);
+    }
+
+    const ContentCache *getContentCache() const {
+      return ContentAndKind.getPointer();
+    }
+
+    /// Return whether this is a system header or not.
+    CharacteristicKind getFileCharacteristic() const {
+      return ContentAndKind.getInt();
+    }
+
+    /// Return true if this FileID has \#line directives in it.
+    bool hasLineDirectives() const { return HasLineDirectives; }
+
+    /// Set the flag that indicates that this FileID has
+    /// line table entries associated with it.
+    void setHasLineDirectives() {
+      HasLineDirectives = true;
+    }
+  };
+
+  /// Each ExpansionInfo encodes the expansion location - where
+  /// the token was ultimately expanded, and the SpellingLoc - where the actual
+  /// character data for the token came from.
+  class ExpansionInfo {
+    // Really these are all SourceLocations.
+
+    /// Where the spelling for the token can be found.
+    unsigned SpellingLoc;
+
+    /// In a macro expansion, ExpansionLocStart and ExpansionLocEnd
+    /// indicate the start and end of the expansion. In object-like macros,
+    /// they will be the same. In a function-like macro expansion, the start
+    /// will be the identifier and the end will be the ')'. Finally, in
+    /// macro-argument instantiations, the end will be 'SourceLocation()', an
+    /// invalid location.
+    unsigned ExpansionLocStart, ExpansionLocEnd;
+
+    /// Whether the expansion range is a token range.
+    bool ExpansionIsTokenRange;
+
+  public:
+    SourceLocation getSpellingLoc() const {
+      SourceLocation SpellLoc = SourceLocation::getFromRawEncoding(SpellingLoc);
+      return SpellLoc.isInvalid() ? getExpansionLocStart() : SpellLoc;
+    }
+
+    SourceLocation getExpansionLocStart() const {
+      return SourceLocation::getFromRawEncoding(ExpansionLocStart);
+    }
+
+    SourceLocation getExpansionLocEnd() const {
+      SourceLocation EndLoc =
+        SourceLocation::getFromRawEncoding(ExpansionLocEnd);
+      return EndLoc.isInvalid() ? getExpansionLocStart() : EndLoc;
+    }
+
+    bool isExpansionTokenRange() const {
+      return ExpansionIsTokenRange;
+    }
+
+    CharSourceRange getExpansionLocRange() const {
+      return CharSourceRange(
+          SourceRange(getExpansionLocStart(), getExpansionLocEnd()),
+          isExpansionTokenRange());
+    }
+
+    bool isMacroArgExpansion() const {
+      // Note that this needs to return false for default constructed objects.
+      return getExpansionLocStart().isValid() &&
+        SourceLocation::getFromRawEncoding(ExpansionLocEnd).isInvalid();
+    }
+
+    bool isMacroBodyExpansion() const {
+      return getExpansionLocStart().isValid() &&
+        SourceLocation::getFromRawEncoding(ExpansionLocEnd).isValid();
+    }
+
+    bool isFunctionMacroExpansion() const {
+      return getExpansionLocStart().isValid() &&
+          getExpansionLocStart() != getExpansionLocEnd();
+    }
+
+    /// Return a ExpansionInfo for an expansion.
+    ///
+    /// Start and End specify the expansion range (where the macro is
+    /// expanded), and SpellingLoc specifies the spelling location (where
+    /// the characters from the token come from). All three can refer to
+    /// normal File SLocs or expansion locations.
+    static ExpansionInfo create(SourceLocation SpellingLoc,
+                                SourceLocation Start, SourceLocation End,
+                                bool ExpansionIsTokenRange = true) {
+      ExpansionInfo X;
+      X.SpellingLoc = SpellingLoc.getRawEncoding();
+      X.ExpansionLocStart = Start.getRawEncoding();
+      X.ExpansionLocEnd = End.getRawEncoding();
+      X.ExpansionIsTokenRange = ExpansionIsTokenRange;
+      return X;
+    }
+
+    /// Return a special ExpansionInfo for the expansion of
+    /// a macro argument into a function-like macro's body.
+    ///
+    /// ExpansionLoc specifies the expansion location (where the macro is
+    /// expanded). This doesn't need to be a range because a macro is always
+    /// expanded at a macro parameter reference, and macro parameters are
+    /// always exactly one token. SpellingLoc specifies the spelling location
+    /// (where the characters from the token come from). ExpansionLoc and
+    /// SpellingLoc can both refer to normal File SLocs or expansion locations.
+    ///
+    /// Given the code:
+    /// \code
+    ///   #define F(x) f(x)
+    ///   F(42);
+    /// \endcode
+    ///
+    /// When expanding '\c F(42)', the '\c x' would call this with an
+    /// SpellingLoc pointing at '\c 42' and an ExpansionLoc pointing at its
+    /// location in the definition of '\c F'.
+    static ExpansionInfo createForMacroArg(SourceLocation SpellingLoc,
+                                           SourceLocation ExpansionLoc) {
+      // We store an intentionally invalid source location for the end of the
+      // expansion range to mark that this is a macro argument location rather
+      // than a normal one.
+      return create(SpellingLoc, ExpansionLoc, SourceLocation());
+    }
+
+    /// Return a special ExpansionInfo representing a token that ends
+    /// prematurely. This is used to model a '>>' token that has been split
+    /// into '>' tokens and similar cases. Unlike for the other forms of
+    /// expansion, the expansion range in this case is a character range, not
+    /// a token range.
+    static ExpansionInfo createForTokenSplit(SourceLocation SpellingLoc,
+                                             SourceLocation Start,
+                                             SourceLocation End) {
+      return create(SpellingLoc, Start, End, false);
+    }
+  };
+
+  /// This is a discriminated union of FileInfo and ExpansionInfo.
+  ///
+  /// SourceManager keeps an array of these objects, and they are uniquely
+  /// identified by the FileID datatype.
+  class SLocEntry {
+    unsigned Offset : 31;
+    unsigned IsExpansion : 1;
+    union {
+      FileInfo File;
+      ExpansionInfo Expansion;
+    };
+
+  public:
+    SLocEntry() : Offset(), IsExpansion(), File() {}
+
+    unsigned getOffset() const { return Offset; }
+
+    bool isExpansion() const { return IsExpansion; }
+    bool isFile() const { return !isExpansion(); }
+
+    const FileInfo &getFile() const {
+      assert(isFile() && "Not a file SLocEntry!");
+      return File;
+    }
+
+    const ExpansionInfo &getExpansion() const {
+      assert(isExpansion() && "Not a macro expansion SLocEntry!");
+      return Expansion;
+    }
+
+    static SLocEntry get(unsigned Offset, const FileInfo &FI) {
+      assert(!(Offset & (1u << 31)) && "Offset is too large");
+      SLocEntry E;
+      E.Offset = Offset;
+      E.IsExpansion = false;
+      E.File = FI;
+      return E;
+    }
+
+    static SLocEntry get(unsigned Offset, const ExpansionInfo &Expansion) {
+      assert(!(Offset & (1u << 31)) && "Offset is too large");
+      SLocEntry E;
+      E.Offset = Offset;
+      E.IsExpansion = true;
+      E.Expansion = Expansion;
+      return E;
+    }
+  };
+
+} // namespace SrcMgr
+
+/// External source of source location entries.
+class ExternalSLocEntrySource {
+public:
+  virtual ~ExternalSLocEntrySource();
+
+  /// Read the source location entry with index ID, which will always be
+  /// less than -1.
+  ///
+  /// \returns true if an error occurred that prevented the source-location
+  /// entry from being loaded.
+  virtual bool ReadSLocEntry(int ID) = 0;
+
+  /// Retrieve the module import location and name for the given ID, if
+  /// in fact it was loaded from a module (rather than, say, a precompiled
+  /// header).
+  virtual std::pair<SourceLocation, StringRef> getModuleImportLoc(int ID) = 0;
+};
+
+/// Holds the cache used by isBeforeInTranslationUnit.
+///
+/// The cache structure is complex enough to be worth breaking out of
+/// SourceManager.
+class InBeforeInTUCacheEntry {
+  /// The FileID's of the cached query.
+  ///
+  /// If these match up with a subsequent query, the result can be reused.
+  FileID LQueryFID, RQueryFID;
+
+  /// True if LQueryFID was created before RQueryFID.
+  ///
+  /// This is used to compare macro expansion locations.
+  bool IsLQFIDBeforeRQFID;
+
+  /// The file found in common between the two \#include traces, i.e.,
+  /// the nearest common ancestor of the \#include tree.
+  FileID CommonFID;
+
+  /// The offset of the previous query in CommonFID.
+  ///
+  /// Usually, this represents the location of the \#include for QueryFID, but
+  /// if LQueryFID is a parent of RQueryFID (or vice versa) then these can be a
+  /// random token in the parent.
+  unsigned LCommonOffset, RCommonOffset;
+
+public:
+  /// Return true if the currently cached values match up with
+  /// the specified LHS/RHS query.
+  ///
+  /// If not, we can't use the cache.
+  bool isCacheValid(FileID LHS, FileID RHS) const {
+    return LQueryFID == LHS && RQueryFID == RHS;
+  }
+
+  /// If the cache is valid, compute the result given the
+  /// specified offsets in the LHS/RHS FileID's.
+  bool getCachedResult(unsigned LOffset, unsigned ROffset) const {
+    // If one of the query files is the common file, use the offset.  Otherwise,
+    // use the #include loc in the common file.
+    if (LQueryFID != CommonFID) LOffset = LCommonOffset;
+    if (RQueryFID != CommonFID) ROffset = RCommonOffset;
+
+    // It is common for multiple macro expansions to be "included" from the same
+    // location (expansion location), in which case use the order of the FileIDs
+    // to determine which came first. This will also take care the case where
+    // one of the locations points at the inclusion/expansion point of the other
+    // in which case its FileID will come before the other.
+    if (LOffset == ROffset)
+      return IsLQFIDBeforeRQFID;
+
+    return LOffset < ROffset;
+  }
+
+  /// Set up a new query.
+  void setQueryFIDs(FileID LHS, FileID RHS, bool isLFIDBeforeRFID) {
+    assert(LHS != RHS);
+    LQueryFID = LHS;
+    RQueryFID = RHS;
+    IsLQFIDBeforeRQFID = isLFIDBeforeRFID;
+  }
+
+  void clear() {
+    LQueryFID = RQueryFID = FileID();
+    IsLQFIDBeforeRQFID = false;
+  }
+
+  void setCommonLoc(FileID commonFID, unsigned lCommonOffset,
+                    unsigned rCommonOffset) {
+    CommonFID = commonFID;
+    LCommonOffset = lCommonOffset;
+    RCommonOffset = rCommonOffset;
+  }
+};
+
+/// The stack used when building modules on demand, which is used
+/// to provide a link between the source managers of the different compiler
+/// instances.
+using ModuleBuildStack = ArrayRef<std::pair<std::string, FullSourceLoc>>;
+
+/// This class handles loading and caching of source files into memory.
+///
+/// This object owns the MemoryBuffer objects for all of the loaded
+/// files and assigns unique FileID's for each unique \#include chain.
+///
+/// The SourceManager can be queried for information about SourceLocation
+/// objects, turning them into either spelling or expansion locations. Spelling
+/// locations represent where the bytes corresponding to a token came from and
+/// expansion locations represent where the location is in the user's view. In
+/// the case of a macro expansion, for example, the spelling location indicates
+/// where the expanded token came from and the expansion location specifies
+/// where it was expanded.
+class SourceManager : public RefCountedBase<SourceManager> {
+  /// DiagnosticsEngine object.
+  DiagnosticsEngine &Diag;
+
+  FileManager &FileMgr;
+
+  mutable llvm::BumpPtrAllocator ContentCacheAlloc;
+
+  /// Memoized information about all of the files tracked by this
+  /// SourceManager.
+  ///
+  /// This map allows us to merge ContentCache entries based
+  /// on their FileEntry*.  All ContentCache objects will thus have unique,
+  /// non-null, FileEntry pointers.
+  llvm::DenseMap<const FileEntry*, SrcMgr::ContentCache*> FileInfos;
+
+  /// True if the ContentCache for files that are overridden by other
+  /// files, should report the original file name. Defaults to true.
+  bool OverridenFilesKeepOriginalName = true;
+
+  /// True if non-system source files should be treated as volatile
+  /// (likely to change while trying to use them). Defaults to false.
+  bool UserFilesAreVolatile;
+
+  /// True if all files read during this compilation should be treated
+  /// as transient (may not be present in later compilations using a module
+  /// file created from this compilation). Defaults to false.
+  bool FilesAreTransient = false;
+
+  struct OverriddenFilesInfoTy {
+    /// Files that have been overridden with the contents from another
+    /// file.
+    llvm::DenseMap<const FileEntry *, const FileEntry *> OverriddenFiles;
+
+    /// Files that were overridden with a memory buffer.
+    llvm::DenseSet<const FileEntry *> OverriddenFilesWithBuffer;
+  };
+
+  /// Lazily create the object keeping overridden files info, since
+  /// it is uncommonly used.
+  std::unique_ptr<OverriddenFilesInfoTy> OverriddenFilesInfo;
+
+  OverriddenFilesInfoTy &getOverriddenFilesInfo() {
+    if (!OverriddenFilesInfo)
+      OverriddenFilesInfo.reset(new OverriddenFilesInfoTy);
+    return *OverriddenFilesInfo;
+  }
+
+  /// Information about various memory buffers that we have read in.
+  ///
+  /// All FileEntry* within the stored ContentCache objects are NULL,
+  /// as they do not refer to a file.
+  std::vector<SrcMgr::ContentCache*> MemBufferInfos;
+
+  /// The table of SLocEntries that are local to this module.
+  ///
+  /// Positive FileIDs are indexes into this table. Entry 0 indicates an invalid
+  /// expansion.
+  SmallVector<SrcMgr::SLocEntry, 0> LocalSLocEntryTable;
+
+  /// The table of SLocEntries that are loaded from other modules.
+  ///
+  /// Negative FileIDs are indexes into this table. To get from ID to an index,
+  /// use (-ID - 2).
+  mutable SmallVector<SrcMgr::SLocEntry, 0> LoadedSLocEntryTable;
+
+  /// The starting offset of the next local SLocEntry.
+  ///
+  /// This is LocalSLocEntryTable.back().Offset + the size of that entry.
+  unsigned NextLocalOffset;
+
+  /// The starting offset of the latest batch of loaded SLocEntries.
+  ///
+  /// This is LoadedSLocEntryTable.back().Offset, except that that entry might
+  /// not have been loaded, so that value would be unknown.
+  unsigned CurrentLoadedOffset;
+
+  /// The highest possible offset is 2^31-1, so CurrentLoadedOffset
+  /// starts at 2^31.
+  static const unsigned MaxLoadedOffset = 1U << 31U;
+
+  /// A bitmap that indicates whether the entries of LoadedSLocEntryTable
+  /// have already been loaded from the external source.
+  ///
+  /// Same indexing as LoadedSLocEntryTable.
+  llvm::BitVector SLocEntryLoaded;
+
+  /// An external source for source location entries.
+  ExternalSLocEntrySource *ExternalSLocEntries = nullptr;
+
+  /// A one-entry cache to speed up getFileID.
+  ///
+  /// LastFileIDLookup records the last FileID looked up or created, because it
+  /// is very common to look up many tokens from the same file.
+  mutable FileID LastFileIDLookup;
+
+  /// Holds information for \#line directives.
+  ///
+  /// This is referenced by indices from SLocEntryTable.
+  LineTableInfo *LineTable = nullptr;
+
+  /// These ivars serve as a cache used in the getLineNumber
+  /// method which is used to speedup getLineNumber calls to nearby locations.
+  mutable FileID LastLineNoFileIDQuery;
+  mutable SrcMgr::ContentCache *LastLineNoContentCache;
+  mutable unsigned LastLineNoFilePos;
+  mutable unsigned LastLineNoResult;
+
+  /// The file ID for the main source file of the translation unit.
+  FileID MainFileID;
+
+  /// The file ID for the precompiled preamble there is one.
+  FileID PreambleFileID;
+
+  // Statistics for -print-stats.
+  mutable unsigned NumLinearScans = 0;
+  mutable unsigned NumBinaryProbes = 0;
+
+  /// Associates a FileID with its "included/expanded in" decomposed
+  /// location.
+  ///
+  /// Used to cache results from and speed-up \c getDecomposedIncludedLoc
+  /// function.
+  mutable llvm::DenseMap<FileID, std::pair<FileID, unsigned>> IncludedLocMap;
+
+  /// The key value into the IsBeforeInTUCache table.
+  using IsBeforeInTUCacheKey = std::pair<FileID, FileID>;
+
+  /// The IsBeforeInTranslationUnitCache is a mapping from FileID pairs
+  /// to cache results.
+  using InBeforeInTUCache =
+      llvm::DenseMap<IsBeforeInTUCacheKey, InBeforeInTUCacheEntry>;
+
+  /// Cache results for the isBeforeInTranslationUnit method.
+  mutable InBeforeInTUCache IBTUCache;
+  mutable InBeforeInTUCacheEntry IBTUCacheOverflow;
+
+  /// Return the cache entry for comparing the given file IDs
+  /// for isBeforeInTranslationUnit.
+  InBeforeInTUCacheEntry &getInBeforeInTUCache(FileID LFID, FileID RFID) const;
+
+  // Cache for the "fake" buffer used for error-recovery purposes.
+  mutable std::unique_ptr<llvm::MemoryBuffer> FakeBufferForRecovery;
+
+  mutable std::unique_ptr<SrcMgr::ContentCache> FakeContentCacheForRecovery;
+
+  /// Lazily computed map of macro argument chunks to their expanded
+  /// source location.
+  using MacroArgsMap = std::map<unsigned, SourceLocation>;
+
+  mutable llvm::DenseMap<FileID, std::unique_ptr<MacroArgsMap>>
+      MacroArgsCacheMap;
+
+  /// The stack of modules being built, which is used to detect
+  /// cycles in the module dependency graph as modules are being built, as
+  /// well as to describe why we're rebuilding a particular module.
+  ///
+  /// There is no way to set this value from the command line. If we ever need
+  /// to do so (e.g., if on-demand module construction moves out-of-process),
+  /// we can add a cc1-level option to do so.
+  SmallVector<std::pair<std::string, FullSourceLoc>, 2> StoredModuleBuildStack;
+
+public:
+  SourceManager(DiagnosticsEngine &Diag, FileManager &FileMgr,
+                bool UserFilesAreVolatile = false);
+  explicit SourceManager(const SourceManager &) = delete;
+  SourceManager &operator=(const SourceManager &) = delete;
+  ~SourceManager();
+
+  void clearIDTables();
+
+  /// Initialize this source manager suitably to replay the compilation
+  /// described by \p Old. Requires that \p Old outlive \p *this.
+  void initializeForReplay(const SourceManager &Old);
+
+  DiagnosticsEngine &getDiagnostics() const { return Diag; }
+
+  FileManager &getFileManager() const { return FileMgr; }
+
+  /// Set true if the SourceManager should report the original file name
+  /// for contents of files that were overridden by other files. Defaults to
+  /// true.
+  void setOverridenFilesKeepOriginalName(bool value) {
+    OverridenFilesKeepOriginalName = value;
+  }
+
+  /// True if non-system source files should be treated as volatile
+  /// (likely to change while trying to use them).
+  bool userFilesAreVolatile() const { return UserFilesAreVolatile; }
+
+  /// Retrieve the module build stack.
+  ModuleBuildStack getModuleBuildStack() const {
+    return StoredModuleBuildStack;
+  }
+
+  /// Set the module build stack.
+  void setModuleBuildStack(ModuleBuildStack stack) {
+    StoredModuleBuildStack.clear();
+    StoredModuleBuildStack.append(stack.begin(), stack.end());
+  }
+
+  /// Push an entry to the module build stack.
+  void pushModuleBuildStack(StringRef moduleName, FullSourceLoc importLoc) {
+    StoredModuleBuildStack.push_back(std::make_pair(moduleName.str(),importLoc));
+  }
+
+  //===--------------------------------------------------------------------===//
+  // MainFileID creation and querying methods.
+  //===--------------------------------------------------------------------===//
+
+  /// Returns the FileID of the main source file.
+  FileID getMainFileID() const { return MainFileID; }
+
+  /// Set the file ID for the main source file.
+  void setMainFileID(FileID FID) {
+    MainFileID = FID;
+  }
+
+  /// Set the file ID for the precompiled preamble.
+  void setPreambleFileID(FileID Preamble) {
+    assert(PreambleFileID.isInvalid() && "PreambleFileID already set!");
+    PreambleFileID = Preamble;
+  }
+
+  /// Get the file ID for the precompiled preamble if there is one.
+  FileID getPreambleFileID() const { return PreambleFileID; }
+
+  //===--------------------------------------------------------------------===//
+  // Methods to create new FileID's and macro expansions.
+  //===--------------------------------------------------------------------===//
+
+  /// Create a new FileID that represents the specified file
+  /// being \#included from the specified IncludePosition.
+  ///
+  /// This translates NULL into standard input.
+  FileID createFileID(const FileEntry *SourceFile, SourceLocation IncludePos,
+                      SrcMgr::CharacteristicKind FileCharacter,
+                      int LoadedID = 0, unsigned LoadedOffset = 0) {
+    const SrcMgr::ContentCache *IR =
+        getOrCreateContentCache(SourceFile, isSystem(FileCharacter));
+    assert(IR && "getOrCreateContentCache() cannot return NULL");
+    return createFileID(IR, IncludePos, FileCharacter, LoadedID, LoadedOffset);
+  }
+
+  /// Create a new FileID that represents the specified memory buffer.
+  ///
+  /// This does no caching of the buffer and takes ownership of the
+  /// MemoryBuffer, so only pass a MemoryBuffer to this once.
+  FileID createFileID(std::unique_ptr<llvm::MemoryBuffer> Buffer,
+                      SrcMgr::CharacteristicKind FileCharacter = SrcMgr::C_User,
+                      int LoadedID = 0, unsigned LoadedOffset = 0,
+                      SourceLocation IncludeLoc = SourceLocation()) {
+    return createFileID(
+        createMemBufferContentCache(Buffer.release(), /*DoNotFree*/ false),
+        IncludeLoc, FileCharacter, LoadedID, LoadedOffset);
+  }
+
+  enum UnownedTag { Unowned };
+
+  /// Create a new FileID that represents the specified memory buffer.
+  ///
+  /// This does no caching of the buffer and takes ownership of the
+  /// MemoryBuffer, so only pass a MemoryBuffer to this once.
+  FileID createFileID(UnownedTag, llvm::MemoryBuffer *Buffer,
+                      SrcMgr::CharacteristicKind FileCharacter = SrcMgr::C_User,
+                      int LoadedID = 0, unsigned LoadedOffset = 0,
+                      SourceLocation IncludeLoc = SourceLocation()) {
+    return createFileID(createMemBufferContentCache(Buffer, /*DoNotFree*/true),
+                        IncludeLoc, FileCharacter, LoadedID, LoadedOffset);
+  }
+
+  /// Get the FileID for \p SourceFile if it exists. Otherwise, create a
+  /// new FileID for the \p SourceFile.
+  FileID getOrCreateFileID(const FileEntry *SourceFile,
+                           SrcMgr::CharacteristicKind FileCharacter) {
+    FileID ID = translateFile(SourceFile);
+    return ID.isValid() ? ID : createFileID(SourceFile, SourceLocation(),
+                                            FileCharacter);
+  }
+
+  /// Return a new SourceLocation that encodes the
+  /// fact that a token from SpellingLoc should actually be referenced from
+  /// ExpansionLoc, and that it represents the expansion of a macro argument
+  /// into the function-like macro body.
+  SourceLocation createMacroArgExpansionLoc(SourceLocation Loc,
+                                            SourceLocation ExpansionLoc,
+                                            unsigned TokLength);
+
+  /// Return a new SourceLocation that encodes the fact
+  /// that a token from SpellingLoc should actually be referenced from
+  /// ExpansionLoc.
+  SourceLocation createExpansionLoc(SourceLocation Loc,
+                                    SourceLocation ExpansionLocStart,
+                                    SourceLocation ExpansionLocEnd,
+                                    unsigned TokLength,
+                                    bool ExpansionIsTokenRange = true,
+                                    int LoadedID = 0,
+                                    unsigned LoadedOffset = 0);
+
+  /// Return a new SourceLocation that encodes that the token starting
+  /// at \p TokenStart ends prematurely at \p TokenEnd.
+  SourceLocation createTokenSplitLoc(SourceLocation SpellingLoc,
+                                     SourceLocation TokenStart,
+                                     SourceLocation TokenEnd);
+
+  /// Retrieve the memory buffer associated with the given file.
+  ///
+  /// \param Invalid If non-NULL, will be set \c true if an error
+  /// occurs while retrieving the memory buffer.
+  llvm::MemoryBuffer *getMemoryBufferForFile(const FileEntry *File,
+                                             bool *Invalid = nullptr);
+
+  /// Override the contents of the given source file by providing an
+  /// already-allocated buffer.
+  ///
+  /// \param SourceFile the source file whose contents will be overridden.
+  ///
+  /// \param Buffer the memory buffer whose contents will be used as the
+  /// data in the given source file.
+  ///
+  /// \param DoNotFree If true, then the buffer will not be freed when the
+  /// source manager is destroyed.
+  void overrideFileContents(const FileEntry *SourceFile,
+                            llvm::MemoryBuffer *Buffer, bool DoNotFree);
+  void overrideFileContents(const FileEntry *SourceFile,
+                            std::unique_ptr<llvm::MemoryBuffer> Buffer) {
+    overrideFileContents(SourceFile, Buffer.release(), /*DoNotFree*/ false);
+  }
+
+  /// Override the given source file with another one.
+  ///
+  /// \param SourceFile the source file which will be overridden.
+  ///
+  /// \param NewFile the file whose contents will be used as the
+  /// data instead of the contents of the given source file.
+  void overrideFileContents(const FileEntry *SourceFile,
+                            const FileEntry *NewFile);
+
+  /// Returns true if the file contents have been overridden.
+  bool isFileOverridden(const FileEntry *File) const {
+    if (OverriddenFilesInfo) {
+      if (OverriddenFilesInfo->OverriddenFilesWithBuffer.count(File))
+        return true;
+      if (OverriddenFilesInfo->OverriddenFiles.find(File) !=
+          OverriddenFilesInfo->OverriddenFiles.end())
+        return true;
+    }
+    return false;
+  }
+
+  /// Disable overridding the contents of a file, previously enabled
+  /// with #overrideFileContents.
+  ///
+  /// This should be called before parsing has begun.
+  void disableFileContentsOverride(const FileEntry *File);
+
+  /// Specify that a file is transient.
+  void setFileIsTransient(const FileEntry *SourceFile);
+
+  /// Specify that all files that are read during this compilation are
+  /// transient.
+  void setAllFilesAreTransient(bool Transient) {
+    FilesAreTransient = Transient;
+  }
+
+  //===--------------------------------------------------------------------===//
+  // FileID manipulation methods.
+  //===--------------------------------------------------------------------===//
+
+  /// Return the buffer for the specified FileID.
+  ///
+  /// If there is an error opening this buffer the first time, this
+  /// manufactures a temporary buffer and returns a non-empty error string.
+  llvm::MemoryBuffer *getBuffer(FileID FID, SourceLocation Loc,
+                                bool *Invalid = nullptr) const {
+    bool MyInvalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &MyInvalid);
+    if (MyInvalid || !Entry.isFile()) {
+      if (Invalid)
+        *Invalid = true;
+
+      return getFakeBufferForRecovery();
+    }
+
+    return Entry.getFile().getContentCache()->getBuffer(Diag, *this, Loc,
+                                                        Invalid);
+  }
+
+  llvm::MemoryBuffer *getBuffer(FileID FID, bool *Invalid = nullptr) const {
+    bool MyInvalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &MyInvalid);
+    if (MyInvalid || !Entry.isFile()) {
+      if (Invalid)
+        *Invalid = true;
+
+      return getFakeBufferForRecovery();
+    }
+
+    return Entry.getFile().getContentCache()->getBuffer(Diag, *this,
+                                                        SourceLocation(),
+                                                        Invalid);
+  }
+
+  /// Returns the FileEntry record for the provided FileID.
+  const FileEntry *getFileEntryForID(FileID FID) const {
+    bool MyInvalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &MyInvalid);
+    if (MyInvalid || !Entry.isFile())
+      return nullptr;
+
+    const SrcMgr::ContentCache *Content = Entry.getFile().getContentCache();
+    if (!Content)
+      return nullptr;
+    return Content->OrigEntry;
+  }
+
+  /// Returns the FileEntry record for the provided SLocEntry.
+  const FileEntry *getFileEntryForSLocEntry(const SrcMgr::SLocEntry &sloc) const
+  {
+    const SrcMgr::ContentCache *Content = sloc.getFile().getContentCache();
+    if (!Content)
+      return nullptr;
+    return Content->OrigEntry;
+  }
+
+  /// Return a StringRef to the source buffer data for the
+  /// specified FileID.
+  ///
+  /// \param FID The file ID whose contents will be returned.
+  /// \param Invalid If non-NULL, will be set true if an error occurred.
+  StringRef getBufferData(FileID FID, bool *Invalid = nullptr) const;
+
+  /// Get the number of FileIDs (files and macros) that were created
+  /// during preprocessing of \p FID, including it.
+  unsigned getNumCreatedFIDsForFileID(FileID FID) const {
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+    if (Invalid || !Entry.isFile())
+      return 0;
+
+    return Entry.getFile().NumCreatedFIDs;
+  }
+
+  /// Set the number of FileIDs (files and macros) that were created
+  /// during preprocessing of \p FID, including it.
+  void setNumCreatedFIDsForFileID(FileID FID, unsigned NumFIDs,
+                                  bool Force = false) const {
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+    if (Invalid || !Entry.isFile())
+      return;
+
+    assert((Force || Entry.getFile().NumCreatedFIDs == 0) && "Already set!");
+    const_cast<SrcMgr::FileInfo &>(Entry.getFile()).NumCreatedFIDs = NumFIDs;
+  }
+
+  //===--------------------------------------------------------------------===//
+  // SourceLocation manipulation methods.
+  //===--------------------------------------------------------------------===//
+
+  /// Return the FileID for a SourceLocation.
+  ///
+  /// This is a very hot method that is used for all SourceManager queries
+  /// that start with a SourceLocation object.  It is responsible for finding
+  /// the entry in SLocEntryTable which contains the specified location.
+  ///
+  FileID getFileID(SourceLocation SpellingLoc) const {
+    unsigned SLocOffset = SpellingLoc.getOffset();
+
+    // If our one-entry cache covers this offset, just return it.
+    if (isOffsetInFileID(LastFileIDLookup, SLocOffset))
+      return LastFileIDLookup;
+
+    return getFileIDSlow(SLocOffset);
+  }
+
+  /// Return the filename of the file containing a SourceLocation.
+  StringRef getFilename(SourceLocation SpellingLoc) const {
+    if (const FileEntry *F = getFileEntryForID(getFileID(SpellingLoc)))
+      return F->getName();
+    return StringRef();
+  }
+
+  /// Return the source location corresponding to the first byte of
+  /// the specified file.
+  SourceLocation getLocForStartOfFile(FileID FID) const {
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+    if (Invalid || !Entry.isFile())
+      return SourceLocation();
+
+    unsigned FileOffset = Entry.getOffset();
+    return SourceLocation::getFileLoc(FileOffset);
+  }
+
+  /// Return the source location corresponding to the last byte of the
+  /// specified file.
+  SourceLocation getLocForEndOfFile(FileID FID) const {
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+    if (Invalid || !Entry.isFile())
+      return SourceLocation();
+
+    unsigned FileOffset = Entry.getOffset();
+    return SourceLocation::getFileLoc(FileOffset + getFileIDSize(FID));
+  }
+
+  /// Returns the include location if \p FID is a \#include'd file
+  /// otherwise it returns an invalid location.
+  SourceLocation getIncludeLoc(FileID FID) const {
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+    if (Invalid || !Entry.isFile())
+      return SourceLocation();
+
+    return Entry.getFile().getIncludeLoc();
+  }
+
+  // Returns the import location if the given source location is
+  // located within a module, or an invalid location if the source location
+  // is within the current translation unit.
+  std::pair<SourceLocation, StringRef>
+  getModuleImportLoc(SourceLocation Loc) const {
+    FileID FID = getFileID(Loc);
+
+    // Positive file IDs are in the current translation unit, and -1 is a
+    // placeholder.
+    if (FID.ID >= -1)
+      return std::make_pair(SourceLocation(), "");
+
+    return ExternalSLocEntries->getModuleImportLoc(FID.ID);
+  }
+
+  /// Given a SourceLocation object \p Loc, return the expansion
+  /// location referenced by the ID.
+  SourceLocation getExpansionLoc(SourceLocation Loc) const {
+    // Handle the non-mapped case inline, defer to out of line code to handle
+    // expansions.
+    if (Loc.isFileID()) return Loc;
+    return getExpansionLocSlowCase(Loc);
+  }
+
+  /// Given \p Loc, if it is a macro location return the expansion
+  /// location or the spelling location, depending on if it comes from a
+  /// macro argument or not.
+  SourceLocation getFileLoc(SourceLocation Loc) const {
+    if (Loc.isFileID()) return Loc;
+    return getFileLocSlowCase(Loc);
+  }
+
+  /// Return the start/end of the expansion information for an
+  /// expansion location.
+  ///
+  /// \pre \p Loc is required to be an expansion location.
+  CharSourceRange getImmediateExpansionRange(SourceLocation Loc) const;
+
+  /// Given a SourceLocation object, return the range of
+  /// tokens covered by the expansion in the ultimate file.
+  CharSourceRange getExpansionRange(SourceLocation Loc) const;
+
+  /// Given a SourceRange object, return the range of
+  /// tokens or characters covered by the expansion in the ultimate file.
+  CharSourceRange getExpansionRange(SourceRange Range) const {
+    SourceLocation Begin = getExpansionRange(Range.getBegin()).getBegin();
+    CharSourceRange End = getExpansionRange(Range.getEnd());
+    return CharSourceRange(SourceRange(Begin, End.getEnd()),
+                           End.isTokenRange());
+  }
+
+  /// Given a CharSourceRange object, return the range of
+  /// tokens or characters covered by the expansion in the ultimate file.
+  CharSourceRange getExpansionRange(CharSourceRange Range) const {
+    CharSourceRange Expansion = getExpansionRange(Range.getAsRange());
+    if (Expansion.getEnd() == Range.getEnd())
+      Expansion.setTokenRange(Range.isTokenRange());
+    return Expansion;
+  }
+
+  /// Given a SourceLocation object, return the spelling
+  /// location referenced by the ID.
+  ///
+  /// This is the place where the characters that make up the lexed token
+  /// can be found.
+  SourceLocation getSpellingLoc(SourceLocation Loc) const {
+    // Handle the non-mapped case inline, defer to out of line code to handle
+    // expansions.
+    if (Loc.isFileID()) return Loc;
+    return getSpellingLocSlowCase(Loc);
+  }
+
+  /// Given a SourceLocation object, return the spelling location
+  /// referenced by the ID.
+  ///
+  /// This is the first level down towards the place where the characters
+  /// that make up the lexed token can be found.  This should not generally
+  /// be used by clients.
+  SourceLocation getImmediateSpellingLoc(SourceLocation Loc) const;
+
+  /// Form a SourceLocation from a FileID and Offset pair.
+  SourceLocation getComposedLoc(FileID FID, unsigned Offset) const {
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+    if (Invalid)
+      return SourceLocation();
+
+    unsigned GlobalOffset = Entry.getOffset() + Offset;
+    return Entry.isFile() ? SourceLocation::getFileLoc(GlobalOffset)
+                          : SourceLocation::getMacroLoc(GlobalOffset);
+  }
+
+  /// Decompose the specified location into a raw FileID + Offset pair.
+  ///
+  /// The first element is the FileID, the second is the offset from the
+  /// start of the buffer of the location.
+  std::pair<FileID, unsigned> getDecomposedLoc(SourceLocation Loc) const {
+    FileID FID = getFileID(Loc);
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &E = getSLocEntry(FID, &Invalid);
+    if (Invalid)
+      return std::make_pair(FileID(), 0);
+    return std::make_pair(FID, Loc.getOffset()-E.getOffset());
+  }
+
+  /// Decompose the specified location into a raw FileID + Offset pair.
+  ///
+  /// If the location is an expansion record, walk through it until we find
+  /// the final location expanded.
+  std::pair<FileID, unsigned>
+  getDecomposedExpansionLoc(SourceLocation Loc) const {
+    FileID FID = getFileID(Loc);
+    bool Invalid = false;
+    const SrcMgr::SLocEntry *E = &getSLocEntry(FID, &Invalid);
+    if (Invalid)
+      return std::make_pair(FileID(), 0);
+
+    unsigned Offset = Loc.getOffset()-E->getOffset();
+    if (Loc.isFileID())
+      return std::make_pair(FID, Offset);
+
+    return getDecomposedExpansionLocSlowCase(E);
+  }
+
+  /// Decompose the specified location into a raw FileID + Offset pair.
+  ///
+  /// If the location is an expansion record, walk through it until we find
+  /// its spelling record.
+  std::pair<FileID, unsigned>
+  getDecomposedSpellingLoc(SourceLocation Loc) const {
+    FileID FID = getFileID(Loc);
+    bool Invalid = false;
+    const SrcMgr::SLocEntry *E = &getSLocEntry(FID, &Invalid);
+    if (Invalid)
+      return std::make_pair(FileID(), 0);
+
+    unsigned Offset = Loc.getOffset()-E->getOffset();
+    if (Loc.isFileID())
+      return std::make_pair(FID, Offset);
+    return getDecomposedSpellingLocSlowCase(E, Offset);
+  }
+
+  /// Returns the "included/expanded in" decomposed location of the given
+  /// FileID.
+  std::pair<FileID, unsigned> getDecomposedIncludedLoc(FileID FID) const;
+
+  /// Returns the offset from the start of the file that the
+  /// specified SourceLocation represents.
+  ///
+  /// This is not very meaningful for a macro ID.
+  unsigned getFileOffset(SourceLocation SpellingLoc) const {
+    return getDecomposedLoc(SpellingLoc).second;
+  }
+
+  /// Tests whether the given source location represents a macro
+  /// argument's expansion into the function-like macro definition.
+  ///
+  /// \param StartLoc If non-null and function returns true, it is set to the
+  /// start location of the macro argument expansion.
+  ///
+  /// Such source locations only appear inside of the expansion
+  /// locations representing where a particular function-like macro was
+  /// expanded.
+  bool isMacroArgExpansion(SourceLocation Loc,
+                           SourceLocation *StartLoc = nullptr) const;
+
+  /// Tests whether the given source location represents the expansion of
+  /// a macro body.
+  ///
+  /// This is equivalent to testing whether the location is part of a macro
+  /// expansion but not the expansion of an argument to a function-like macro.
+  bool isMacroBodyExpansion(SourceLocation Loc) const;
+
+  /// Returns true if the given MacroID location points at the beginning
+  /// of the immediate macro expansion.
+  ///
+  /// \param MacroBegin If non-null and function returns true, it is set to the
+  /// begin location of the immediate macro expansion.
+  bool isAtStartOfImmediateMacroExpansion(SourceLocation Loc,
+                                    SourceLocation *MacroBegin = nullptr) const;
+
+  /// Returns true if the given MacroID location points at the character
+  /// end of the immediate macro expansion.
+  ///
+  /// \param MacroEnd If non-null and function returns true, it is set to the
+  /// character end location of the immediate macro expansion.
+  bool
+  isAtEndOfImmediateMacroExpansion(SourceLocation Loc,
+                                   SourceLocation *MacroEnd = nullptr) const;
+
+  /// Returns true if \p Loc is inside the [\p Start, +\p Length)
+  /// chunk of the source location address space.
+  ///
+  /// If it's true and \p RelativeOffset is non-null, it will be set to the
+  /// relative offset of \p Loc inside the chunk.
+  bool isInSLocAddrSpace(SourceLocation Loc,
+                         SourceLocation Start, unsigned Length,
+                         unsigned *RelativeOffset = nullptr) const {
+    assert(((Start.getOffset() < NextLocalOffset &&
+               Start.getOffset()+Length <= NextLocalOffset) ||
+            (Start.getOffset() >= CurrentLoadedOffset &&
+                Start.getOffset()+Length < MaxLoadedOffset)) &&
+           "Chunk is not valid SLoc address space");
+    unsigned LocOffs = Loc.getOffset();
+    unsigned BeginOffs = Start.getOffset();
+    unsigned EndOffs = BeginOffs + Length;
+    if (LocOffs >= BeginOffs && LocOffs < EndOffs) {
+      if (RelativeOffset)
+        *RelativeOffset = LocOffs - BeginOffs;
+      return true;
+    }
+
+    return false;
+  }
+
+  /// Return true if both \p LHS and \p RHS are in the local source
+  /// location address space or the loaded one.
+  ///
+  /// If it's true and \p RelativeOffset is non-null, it will be set to the
+  /// offset of \p RHS relative to \p LHS.
+  bool isInSameSLocAddrSpace(SourceLocation LHS, SourceLocation RHS,
+                             int *RelativeOffset) const {
+    unsigned LHSOffs = LHS.getOffset(), RHSOffs = RHS.getOffset();
+    bool LHSLoaded = LHSOffs >= CurrentLoadedOffset;
+    bool RHSLoaded = RHSOffs >= CurrentLoadedOffset;
+
+    if (LHSLoaded == RHSLoaded) {
+      if (RelativeOffset)
+        *RelativeOffset = RHSOffs - LHSOffs;
+      return true;
+    }
+
+    return false;
+  }
+
+  //===--------------------------------------------------------------------===//
+  // Queries about the code at a SourceLocation.
+  //===--------------------------------------------------------------------===//
+
+  /// Return a pointer to the start of the specified location
+  /// in the appropriate spelling MemoryBuffer.
+  ///
+  /// \param Invalid If non-NULL, will be set \c true if an error occurs.
+  const char *getCharacterData(SourceLocation SL,
+                               bool *Invalid = nullptr) const;
+
+  /// Return the column # for the specified file position.
+  ///
+  /// This is significantly cheaper to compute than the line number.  This
+  /// returns zero if the column number isn't known.  This may only be called
+  /// on a file sloc, so you must choose a spelling or expansion location
+  /// before calling this method.
+  unsigned getColumnNumber(FileID FID, unsigned FilePos,
+                           bool *Invalid = nullptr) const;
+  unsigned getSpellingColumnNumber(SourceLocation Loc,
+                                   bool *Invalid = nullptr) const;
+  unsigned getExpansionColumnNumber(SourceLocation Loc,
+                                    bool *Invalid = nullptr) const;
+  unsigned getPresumedColumnNumber(SourceLocation Loc,
+                                   bool *Invalid = nullptr) const;
+
+  /// Given a SourceLocation, return the spelling line number
+  /// for the position indicated.
+  ///
+  /// This requires building and caching a table of line offsets for the
+  /// MemoryBuffer, so this is not cheap: use only when about to emit a
+  /// diagnostic.
+  unsigned getLineNumber(FileID FID, unsigned FilePos, bool *Invalid = nullptr) const;
+  unsigned getSpellingLineNumber(SourceLocation Loc, bool *Invalid = nullptr) const;
+  unsigned getExpansionLineNumber(SourceLocation Loc, bool *Invalid = nullptr) const;
+  unsigned getPresumedLineNumber(SourceLocation Loc, bool *Invalid = nullptr) const;
+
+  /// Return the filename or buffer identifier of the buffer the
+  /// location is in.
+  ///
+  /// Note that this name does not respect \#line directives.  Use
+  /// getPresumedLoc for normal clients.
+  StringRef getBufferName(SourceLocation Loc, bool *Invalid = nullptr) const;
+
+  /// Return the file characteristic of the specified source
+  /// location, indicating whether this is a normal file, a system
+  /// header, or an "implicit extern C" system header.
+  ///
+  /// This state can be modified with flags on GNU linemarker directives like:
+  /// \code
+  ///   # 4 "foo.h" 3
+  /// \endcode
+  /// which changes all source locations in the current file after that to be
+  /// considered to be from a system header.
+  SrcMgr::CharacteristicKind getFileCharacteristic(SourceLocation Loc) const;
+
+  /// Returns the "presumed" location of a SourceLocation specifies.
+  ///
+  /// A "presumed location" can be modified by \#line or GNU line marker
+  /// directives.  This provides a view on the data that a user should see
+  /// in diagnostics, for example.
+  ///
+  /// Note that a presumed location is always given as the expansion point of
+  /// an expansion location, not at the spelling location.
+  ///
+  /// \returns The presumed location of the specified SourceLocation. If the
+  /// presumed location cannot be calculated (e.g., because \p Loc is invalid
+  /// or the file containing \p Loc has changed on disk), returns an invalid
+  /// presumed location.
+  PresumedLoc getPresumedLoc(SourceLocation Loc,
+                             bool UseLineDirectives = true) const;
+
+  /// Returns whether the PresumedLoc for a given SourceLocation is
+  /// in the main file.
+  ///
+  /// This computes the "presumed" location for a SourceLocation, then checks
+  /// whether it came from a file other than the main file. This is different
+  /// from isWrittenInMainFile() because it takes line marker directives into
+  /// account.
+  bool isInMainFile(SourceLocation Loc) const;
+
+  /// Returns true if the spelling locations for both SourceLocations
+  /// are part of the same file buffer.
+  ///
+  /// This check ignores line marker directives.
+  bool isWrittenInSameFile(SourceLocation Loc1, SourceLocation Loc2) const {
+    return getFileID(Loc1) == getFileID(Loc2);
+  }
+
+  /// Returns true if the spelling location for the given location
+  /// is in the main file buffer.
+  ///
+  /// This check ignores line marker directives.
+  bool isWrittenInMainFile(SourceLocation Loc) const {
+    return getFileID(Loc) == getMainFileID();
+  }
+
+  /// Returns whether \p Loc is located in a <built-in> file.
+  bool isWrittenInBuiltinFile(SourceLocation Loc) const {
+    StringRef Filename(getPresumedLoc(Loc).getFilename());
+    return Filename.equals("<built-in>");
+  }
+
+  /// Returns whether \p Loc is located in a <command line> file.
+  bool isWrittenInCommandLineFile(SourceLocation Loc) const {
+    StringRef Filename(getPresumedLoc(Loc).getFilename());
+    return Filename.equals("<command line>");
+  }
+
+  /// Returns whether \p Loc is located in a <scratch space> file.
+  bool isWrittenInScratchSpace(SourceLocation Loc) const {
+    StringRef Filename(getPresumedLoc(Loc).getFilename());
+    return Filename.equals("<scratch space>");
+  }
+
+  /// Returns if a SourceLocation is in a system header.
+  bool isInSystemHeader(SourceLocation Loc) const {
+    return isSystem(getFileCharacteristic(Loc));
+  }
+
+  /// Returns if a SourceLocation is in an "extern C" system header.
+  bool isInExternCSystemHeader(SourceLocation Loc) const {
+    return getFileCharacteristic(Loc) == SrcMgr::C_ExternCSystem;
+  }
+
+  /// Returns whether \p Loc is expanded from a macro in a system header.
+  bool isInSystemMacro(SourceLocation loc) const {
+    if (!loc.isMacroID())
+      return false;
+
+    // This happens when the macro is the result of a paste, in that case
+    // its spelling is the scratch memory, so we take the parent context.
+    if (isWrittenInScratchSpace(getSpellingLoc(loc)))
+      return isInSystemHeader(getSpellingLoc(getImmediateMacroCallerLoc(loc)));
+
+    return isInSystemHeader(getSpellingLoc(loc));
+  }
+
+  /// The size of the SLocEntry that \p FID represents.
+  unsigned getFileIDSize(FileID FID) const;
+
+  /// Given a specific FileID, returns true if \p Loc is inside that
+  /// FileID chunk and sets relative offset (offset of \p Loc from beginning
+  /// of FileID) to \p relativeOffset.
+  bool isInFileID(SourceLocation Loc, FileID FID,
+                  unsigned *RelativeOffset = nullptr) const {
+    unsigned Offs = Loc.getOffset();
+    if (isOffsetInFileID(FID, Offs)) {
+      if (RelativeOffset)
+        *RelativeOffset = Offs - getSLocEntry(FID).getOffset();
+      return true;
+    }
+
+    return false;
+  }
+
+  //===--------------------------------------------------------------------===//
+  // Line Table Manipulation Routines
+  //===--------------------------------------------------------------------===//
+
+  /// Return the uniqued ID for the specified filename.
+  unsigned getLineTableFilenameID(StringRef Str);
+
+  /// Add a line note to the line table for the FileID and offset
+  /// specified by Loc.
+  ///
+  /// If FilenameID is -1, it is considered to be unspecified.
+  void AddLineNote(SourceLocation Loc, unsigned LineNo, int FilenameID,
+                   bool IsFileEntry, bool IsFileExit,
+                   SrcMgr::CharacteristicKind FileKind);
+
+  /// Determine if the source manager has a line table.
+  bool hasLineTable() const { return LineTable != nullptr; }
+
+  /// Retrieve the stored line table.
+  LineTableInfo &getLineTable();
+
+  //===--------------------------------------------------------------------===//
+  // Queries for performance analysis.
+  //===--------------------------------------------------------------------===//
+
+  /// Return the total amount of physical memory allocated by the
+  /// ContentCache allocator.
+  size_t getContentCacheSize() const {
+    return ContentCacheAlloc.getTotalMemory();
+  }
+
+  struct MemoryBufferSizes {
+    const size_t malloc_bytes;
+    const size_t mmap_bytes;
+
+    MemoryBufferSizes(size_t malloc_bytes, size_t mmap_bytes)
+      : malloc_bytes(malloc_bytes), mmap_bytes(mmap_bytes) {}
+  };
+
+  /// Return the amount of memory used by memory buffers, breaking down
+  /// by heap-backed versus mmap'ed memory.
+  MemoryBufferSizes getMemoryBufferSizes() const;
+
+  /// Return the amount of memory used for various side tables and
+  /// data structures in the SourceManager.
+  size_t getDataStructureSizes() const;
+
+  //===--------------------------------------------------------------------===//
+  // Other miscellaneous methods.
+  //===--------------------------------------------------------------------===//
+
+  /// Get the source location for the given file:line:col triplet.
+  ///
+  /// If the source file is included multiple times, the source location will
+  /// be based upon the first inclusion.
+  SourceLocation translateFileLineCol(const FileEntry *SourceFile,
+                                      unsigned Line, unsigned Col) const;
+
+  /// Get the FileID for the given file.
+  ///
+  /// If the source file is included multiple times, the FileID will be the
+  /// first inclusion.
+  FileID translateFile(const FileEntry *SourceFile) const;
+
+  /// Get the source location in \p FID for the given line:col.
+  /// Returns null location if \p FID is not a file SLocEntry.
+  SourceLocation translateLineCol(FileID FID,
+                                  unsigned Line, unsigned Col) const;
+
+  /// If \p Loc points inside a function macro argument, the returned
+  /// location will be the macro location in which the argument was expanded.
+  /// If a macro argument is used multiple times, the expanded location will
+  /// be at the first expansion of the argument.
+  /// e.g.
+  ///   MY_MACRO(foo);
+  ///             ^
+  /// Passing a file location pointing at 'foo', will yield a macro location
+  /// where 'foo' was expanded into.
+  SourceLocation getMacroArgExpandedLocation(SourceLocation Loc) const;
+
+  /// Determines the order of 2 source locations in the translation unit.
+  ///
+  /// \returns true if LHS source location comes before RHS, false otherwise.
+  bool isBeforeInTranslationUnit(SourceLocation LHS, SourceLocation RHS) const;
+
+  /// Determines whether the two decomposed source location is in the
+  ///        same translation unit. As a byproduct, it also calculates the order
+  ///        of the source locations in case they are in the same TU.
+  ///
+  /// \returns Pair of bools the first component is true if the two locations
+  ///          are in the same TU. The second bool is true if the first is true
+  ///          and \p LOffs is before \p ROffs.
+  std::pair<bool, bool>
+  isInTheSameTranslationUnit(std::pair<FileID, unsigned> &LOffs,
+                             std::pair<FileID, unsigned> &ROffs) const;
+
+  /// Determines the order of 2 source locations in the "source location
+  /// address space".
+  bool isBeforeInSLocAddrSpace(SourceLocation LHS, SourceLocation RHS) const {
+    return isBeforeInSLocAddrSpace(LHS, RHS.getOffset());
+  }
+
+  /// Determines the order of a source location and a source location
+  /// offset in the "source location address space".
+  ///
+  /// Note that we always consider source locations loaded from
+  bool isBeforeInSLocAddrSpace(SourceLocation LHS, unsigned RHS) const {
+    unsigned LHSOffset = LHS.getOffset();
+    bool LHSLoaded = LHSOffset >= CurrentLoadedOffset;
+    bool RHSLoaded = RHS >= CurrentLoadedOffset;
+    if (LHSLoaded == RHSLoaded)
+      return LHSOffset < RHS;
+
+    return LHSLoaded;
+  }
+
+  /// Return true if the Point is within Start and End.
+  bool isPointWithin(SourceLocation Location, SourceLocation Start,
+                     SourceLocation End) const {
+    return Location == Start || Location == End ||
+           (isBeforeInTranslationUnit(Start, Location) &&
+            isBeforeInTranslationUnit(Location, End));
+  }
+
+  // Iterators over FileInfos.
+  using fileinfo_iterator =
+      llvm::DenseMap<const FileEntry*, SrcMgr::ContentCache*>::const_iterator;
+
+  fileinfo_iterator fileinfo_begin() const { return FileInfos.begin(); }
+  fileinfo_iterator fileinfo_end() const { return FileInfos.end(); }
+  bool hasFileInfo(const FileEntry *File) const {
+    return FileInfos.find(File) != FileInfos.end();
+  }
+
+  /// Print statistics to stderr.
+  void PrintStats() const;
+
+  void dump() const;
+
+  /// Get the number of local SLocEntries we have.
+  unsigned local_sloc_entry_size() const { return LocalSLocEntryTable.size(); }
+
+  /// Get a local SLocEntry. This is exposed for indexing.
+  const SrcMgr::SLocEntry &getLocalSLocEntry(unsigned Index,
+                                             bool *Invalid = nullptr) const {
+    assert(Index < LocalSLocEntryTable.size() && "Invalid index");
+    return LocalSLocEntryTable[Index];
+  }
+
+  /// Get the number of loaded SLocEntries we have.
+  unsigned loaded_sloc_entry_size() const { return LoadedSLocEntryTable.size();}
+
+  /// Get a loaded SLocEntry. This is exposed for indexing.
+  const SrcMgr::SLocEntry &getLoadedSLocEntry(unsigned Index,
+                                              bool *Invalid = nullptr) const {
+    assert(Index < LoadedSLocEntryTable.size() && "Invalid index");
+    if (SLocEntryLoaded[Index])
+      return LoadedSLocEntryTable[Index];
+    return loadSLocEntry(Index, Invalid);
+  }
+
+  const SrcMgr::SLocEntry &getSLocEntry(FileID FID,
+                                        bool *Invalid = nullptr) const {
+    if (FID.ID == 0 || FID.ID == -1) {
+      if (Invalid) *Invalid = true;
+      return LocalSLocEntryTable[0];
+    }
+    return getSLocEntryByID(FID.ID, Invalid);
+  }
+
+  unsigned getNextLocalOffset() const { return NextLocalOffset; }
+
+  void setExternalSLocEntrySource(ExternalSLocEntrySource *Source) {
+    assert(LoadedSLocEntryTable.empty() &&
+           "Invalidating existing loaded entries");
+    ExternalSLocEntries = Source;
+  }
+
+  /// Allocate a number of loaded SLocEntries, which will be actually
+  /// loaded on demand from the external source.
+  ///
+  /// NumSLocEntries will be allocated, which occupy a total of TotalSize space
+  /// in the global source view. The lowest ID and the base offset of the
+  /// entries will be returned.
+  std::pair<int, unsigned>
+  AllocateLoadedSLocEntries(unsigned NumSLocEntries, unsigned TotalSize);
+
+  /// Returns true if \p Loc came from a PCH/Module.
+  bool isLoadedSourceLocation(SourceLocation Loc) const {
+    return Loc.getOffset() >= CurrentLoadedOffset;
+  }
+
+  /// Returns true if \p Loc did not come from a PCH/Module.
+  bool isLocalSourceLocation(SourceLocation Loc) const {
+    return Loc.getOffset() < NextLocalOffset;
+  }
+
+  /// Returns true if \p FID came from a PCH/Module.
+  bool isLoadedFileID(FileID FID) const {
+    assert(FID.ID != -1 && "Using FileID sentinel value");
+    return FID.ID < 0;
+  }
+
+  /// Returns true if \p FID did not come from a PCH/Module.
+  bool isLocalFileID(FileID FID) const {
+    return !isLoadedFileID(FID);
+  }
+
+  /// Gets the location of the immediate macro caller, one level up the stack
+  /// toward the initial macro typed into the source.
+  SourceLocation getImmediateMacroCallerLoc(SourceLocation Loc) const {
+    if (!Loc.isMacroID()) return Loc;
+
+    // When we have the location of (part of) an expanded parameter, its
+    // spelling location points to the argument as expanded in the macro call,
+    // and therefore is used to locate the macro caller.
+    if (isMacroArgExpansion(Loc))
+      return getImmediateSpellingLoc(Loc);
+
+    // Otherwise, the caller of the macro is located where this macro is
+    // expanded (while the spelling is part of the macro definition).
+    return getImmediateExpansionRange(Loc).getBegin();
+  }
+
+  /// \return Location of the top-level macro caller.
+  SourceLocation getTopMacroCallerLoc(SourceLocation Loc) const;
+
+private:
+  friend class ASTReader;
+  friend class ASTWriter;
+
+  llvm::MemoryBuffer *getFakeBufferForRecovery() const;
+  const SrcMgr::ContentCache *getFakeContentCacheForRecovery() const;
+
+  const SrcMgr::SLocEntry &loadSLocEntry(unsigned Index, bool *Invalid) const;
+
+  /// Get the entry with the given unwrapped FileID.
+  const SrcMgr::SLocEntry &getSLocEntryByID(int ID,
+                                            bool *Invalid = nullptr) const {
+    assert(ID != -1 && "Using FileID sentinel value");
+    if (ID < 0)
+      return getLoadedSLocEntryByID(ID, Invalid);
+    return getLocalSLocEntry(static_cast<unsigned>(ID), Invalid);
+  }
+
+  const SrcMgr::SLocEntry &
+  getLoadedSLocEntryByID(int ID, bool *Invalid = nullptr) const {
+    return getLoadedSLocEntry(static_cast<unsigned>(-ID - 2), Invalid);
+  }
+
+  /// Implements the common elements of storing an expansion info struct into
+  /// the SLocEntry table and producing a source location that refers to it.
+  SourceLocation createExpansionLocImpl(const SrcMgr::ExpansionInfo &Expansion,
+                                        unsigned TokLength,
+                                        int LoadedID = 0,
+                                        unsigned LoadedOffset = 0);
+
+  /// Return true if the specified FileID contains the
+  /// specified SourceLocation offset.  This is a very hot method.
+  inline bool isOffsetInFileID(FileID FID, unsigned SLocOffset) const {
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID);
+    // If the entry is after the offset, it can't contain it.
+    if (SLocOffset < Entry.getOffset()) return false;
+
+    // If this is the very last entry then it does.
+    if (FID.ID == -2)
+      return true;
+
+    // If it is the last local entry, then it does if the location is local.
+    if (FID.ID+1 == static_cast<int>(LocalSLocEntryTable.size()))
+      return SLocOffset < NextLocalOffset;
+
+    // Otherwise, the entry after it has to not include it. This works for both
+    // local and loaded entries.
+    return SLocOffset < getSLocEntryByID(FID.ID+1).getOffset();
+  }
+
+  /// Returns the previous in-order FileID or an invalid FileID if there
+  /// is no previous one.
+  FileID getPreviousFileID(FileID FID) const;
+
+  /// Returns the next in-order FileID or an invalid FileID if there is
+  /// no next one.
+  FileID getNextFileID(FileID FID) const;
+
+  /// Create a new fileID for the specified ContentCache and
+  /// include position.
+  ///
+  /// This works regardless of whether the ContentCache corresponds to a
+  /// file or some other input source.
+  FileID createFileID(const SrcMgr::ContentCache* File,
+                      SourceLocation IncludePos,
+                      SrcMgr::CharacteristicKind DirCharacter,
+                      int LoadedID, unsigned LoadedOffset);
+
+  const SrcMgr::ContentCache *
+    getOrCreateContentCache(const FileEntry *SourceFile,
+                            bool isSystemFile = false);
+
+  /// Create a new ContentCache for the specified  memory buffer.
+  const SrcMgr::ContentCache *
+  createMemBufferContentCache(llvm::MemoryBuffer *Buf, bool DoNotFree);
+
+  FileID getFileIDSlow(unsigned SLocOffset) const;
+  FileID getFileIDLocal(unsigned SLocOffset) const;
+  FileID getFileIDLoaded(unsigned SLocOffset) const;
+
+  SourceLocation getExpansionLocSlowCase(SourceLocation Loc) const;
+  SourceLocation getSpellingLocSlowCase(SourceLocation Loc) const;
+  SourceLocation getFileLocSlowCase(SourceLocation Loc) const;
+
+  std::pair<FileID, unsigned>
+  getDecomposedExpansionLocSlowCase(const SrcMgr::SLocEntry *E) const;
+  std::pair<FileID, unsigned>
+  getDecomposedSpellingLocSlowCase(const SrcMgr::SLocEntry *E,
+                                   unsigned Offset) const;
+  void computeMacroArgsCache(MacroArgsMap &MacroArgsCache, FileID FID) const;
+  void associateFileChunkWithMacroArgExp(MacroArgsMap &MacroArgsCache,
+                                         FileID FID,
+                                         SourceLocation SpellLoc,
+                                         SourceLocation ExpansionLoc,
+                                         unsigned ExpansionLength) const;
+};
+
+/// Comparison function object.
+template<typename T>
+class BeforeThanCompare;
+
+/// Compare two source locations.
+template<>
+class BeforeThanCompare<SourceLocation> {
+  SourceManager &SM;
+
+public:
+  explicit BeforeThanCompare(SourceManager &SM) : SM(SM) {}
+
+  bool operator()(SourceLocation LHS, SourceLocation RHS) const {
+    return SM.isBeforeInTranslationUnit(LHS, RHS);
+  }
+};
+
+/// Compare two non-overlapping source ranges.
+template<>
+class BeforeThanCompare<SourceRange> {
+  SourceManager &SM;
+
+public:
+  explicit BeforeThanCompare(SourceManager &SM) : SM(SM) {}
+
+  bool operator()(SourceRange LHS, SourceRange RHS) const {
+    return SM.isBeforeInTranslationUnit(LHS.getBegin(), RHS.getBegin());
+  }
+};
+
+/// SourceManager and necessary depdencies (e.g. VFS, FileManager) for a single
+/// in-memorty file.
+class SourceManagerForFile {
+public:
+  /// Creates SourceManager and necessary depdencies (e.g. VFS, FileManager).
+  /// The main file in the SourceManager will be \p FileName with \p Content.
+  SourceManagerForFile(StringRef FileName, StringRef Content);
+
+  SourceManager &get() {
+    assert(SourceMgr);
+    return *SourceMgr;
+  }
+
+private:
+  // The order of these fields are important - they should be in the same order
+  // as they are created in `createSourceManagerForFile` so that they can be
+  // deleted in the reverse order as they are created.
+  std::unique_ptr<FileManager> FileMgr;
+  std::unique_ptr<DiagnosticsEngine> Diagnostics;
+  std::unique_ptr<SourceManager> SourceMgr;
+};
+
+} // namespace clang
+
+#endif // LLVM_CLANG_BASIC_SOURCEMANAGER_H